US2773222A - Relay actuating circuit - Google Patents

Description

Dec. 4, 1956 D. M. CHAUVIN 2,773,222

RELAY ACTUATING CIRCUIT Filed May 14, 1954 2 4 Corn Curl Receiver Trans.

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ATTORNEY aired; States Patent 2,773,222 Patented Dec. 4, 1956 RELAY ACTUA'IING CIRCUIT David Qhauvin, Glen Burnie, Mi, assignor to Westinghouse Electric Corporation, East Pittshurgh, Pa, a corporation of Pennsylvania Application lviay 14, 1954, Serial No. 429,956

2 Claims. (Cl. 317-14?) My invention relates to circuits for relay-keying of signal-transmitting systems which employ communication codes comprising dots and dashes or other on-off type signals. In such systems, the dot or dash signal received through a transmission-line or system actuates a solenoidoperated switch or relay. In any such system noise currents and voltages are inevitable, and so the relay must be so designed that it is not actuated to closed position in response to line-currents of the highest noise level, but will hold it securely in closed position as long as the linecurrent stays above a slightly higher current level which the line delivers at the relay whenever the distant operators signal-switch is closed. In short, the switchactuating relay must remain open as long as the transmission-channel current lies below a first level, and remain closed as long as the channel current stays above a second level; and for general economic reasons these two levels should not he too far apart; for example the lower may be not less than eighty percent of the latter.

However, as is well-known in the electrical art, alternating currents of frequencies well-suited to signal-transmission channels are poorly adapted to operation of mechanical relays; hence electron-tube amplifiers are interposed between the transmission channel and the mechanical relay. in these amplifiers, the output current produced by transmission-channel noise currents, which are below the first level mentioned above, must be insufiicient to move the mechanical relay from open-circuit to closedcircuit position; and the output currents produced by channel currents above the second level must be sufficiently large to hold the relay in closed-circuit position in spite of any jarring or mechanical shock it is likely to be subjected to in usual service. The ratio of the current just sufficient to move a mechanical relay to closed position to the current just sufficient to hold the relay closed in the face of usual mechanical shocks should be fairly low it" the relay is to be of an economical design; thus the current sent into the relay from the amplifier output when the transmission-channel current is at the relayclosing value should preferably be not over forty percent of the amplifier output current when the channel current is at the relay-holding value. It will be seen that these relations impose certain requirements on the voltage input vs. current output characteristics of the electron amplifier; that is to say, an increase of about twenty-five percent (i. e. from 89% to 100%) of the input volts must cause an increase of about one hundred and fifty percent (i. e. from 40% to 100%) in output current. One of the principal features of my invention is the provision of an electronic amplifier having such an input vs. output characteristic. Furthermore, unless a rectifier is to be interposed between the amplifier and the relay, the electronic amplifier must be a ll-C. amplifier having these characteristics.

The foregoing will be seen to be tantamount to the requirement that the electronic amplifier shall have an input-voltage (abscissa) vs. output current (ordinate) characteristic of the shape of the curves in Fig. 1 of the input voltage re drawings. The line marked 22 thereon indicates the current which just sufiices to close the relay and the line 21 indicates the minimum current capable of holding the relay closed in spite of any probable mechanical shock or jar to which it is liable in use.

Another requirement is that it be possible to adjust the threshold value of the input signal which results in closure of the keying relay over a range of value that is wide compared with the difference between the line-input voltage which just suflices to close the relay contacts and the line-input voltage which just suffices to hold the relay closed; this difierence, which is proportional to the slope of the rising portion of the curves, I will refer to as the dili'erential.

A further requirement of the amplifier is that the slope of the rising portions of the curves shall be the same throughout the range over which the threshold current is adjustable.

Yet another requirement of the amplifier is that the tendency of the mechanical relay contacts to bounce open when moved from open to closed position should be minimized.

Sue object of my invention is accordingly to produce a new and improved system for closing and opening a mechanical relay in response to intermittent pulses of control voltage.

Another object is to provide a novel arrangement for closing opening a mechanical relay in response to control voltages in which the control voltage required to hold the relay closed against mechanical shock and jar is only ightly less than that which sufiices to move the etc." from open to closed position.

Another object is to provide a new and improved system embodying electronic means for closing and opening a mechanical relay in response to intermittent pulses of control voltage.

Another object is to provide a new and improved system embodying electronic means for closing and opening a mechanical relay in response to intermittent pulses of control voltage derived through rectifying pulsed highfrequency carier current coming in over a transmission line.

Another object is to provide a system embodying an electronic component for closing and opening a mechanical relay in response to control voltages in which the threshold value of the control voltage which just sufiices to move the relay to closed position may be readily adjusted by varying an element in the electronic component.

Another object is to provide a system embodying an electronic component for closing a mechanism in which he e ectronic component shall exert force on he mechanism, thus minimizing any tendency of the latter to bounce on closing.

Another object is to provide a system for closing a mechanism in response to intermittent control voltage pulse: in which the threshold voltage just sufficing to close the mechanism may be adjusted over substantial range without changing the differential.

Another object is to provide an electronic amplifier adapted for closing and opening a mechanism in response to pulses of control voltage which shall have an input voltage vs. output current characteristic having a sharp slope or" output current per input volt over a substantial igc, but practically zero slope of output current .nput volt over lower voltage range.

Another object is to provide an amplifier of the type described in the immediately preceding paragraph in which said lower substantially covers the range of unwanted fluctuations of the lower values of said control voltage.

Another object is to provide an amplifier of the type described in the paragraph before the last in which the value of the control voltage at which said sharp slope begins may be varied at will over a substantial range without varying themagnitude of said slope.

Still another object is to provide-an amplifier of the typedescribed in the second paragraph before the last which shall have a heavily damped output current.

Other objects of my invention will become apparent upon reading the following description, taken in connection with the drawings, in which:

Figure l is a graph useful in explaining the principles of my invention; and

Fig. 2 is a schematic diagram of a keying relay circuit used to illustrate the principles of my invention.

Since 'it is believed that Fig. i has already been suifi ciently described in the foregoing discussion of the invention, attention will be given to the details of Pig. a. Signal or other control variations may be impressed on a transmission system at a control point symbolized by a signal key 1. and these variations may, in ways too wellknown in the arts to require detailed descriptions, control the output of a carrier current transmitter 2 sending modulated energy into a transmission channel symbolized here by the transmission line 3, whence it passes through a suitable receiver 4 whose rectified output voltage is impressed through a suitable resistor 5 on the control electrode 6 of an electron tube 7 having at least two grids, and which preferably is a pentode. The cathode of the tube 7 is grounded and connected to its control grid 6 by a grid condenser 8 and resistor 9. The anode of tube 7 is connected through a resistor 11 to the positive pole 3+ of a direct-current voltage source (not shown) which has its negative pole grounded, and is also connected to the control grid of an electron tube 12, which is preferably a triode.

The cathode of tube 7 is connected through an adjustable resistor 13 and a resistor 14 to the positive pole 13+, and the common junction of resistors 13 and 14 is connected to the screen grid of the tube '7.

The anode of tube 12', is connected through a resistor 15 to the positive terminal 13+, while the cathode of tube 12 is connected to ground through the actuating winding of a mechanism symbolized by a relay 16, in series with a resistor 17. A resistor 18 connects the common junction of relay to and resistor 17 to the positive terminal B+.

The curves of Fig. 1 show the relationship between the input voltage (abscissa) impressed by receiver 4 on control grid 6 of tube '7 and the output current. (ordinate) flowing from tube 12 into relay to. Different individual curves 23 through 26 correspond to different settings of adjustable resistor 13, curve 23 corresponding to a low value of resistor 13 and curves 2%, 25 and 26 to successively higher values.

I have found that by making the resistor 11 large com pared with the plate-resistance Rp of the tube 7 (e. g. of the order or" 0 times Rp of tube 7), so that the anode of tube 7 operates at only a small fraction of the voltage of positive terminal 13+, while making the value at its maximum resistance of resistor 13 only a small fraction (e. g. one-tenth) of the resistance of resistor 14, voltampere characteristics of the desired shape, as shown at 23, 24, 25, 26 in Fig. l, are attained. This relationship of the resistors l1, l3 and 14 is found to produce substantially the same slope in these curves over a substantial range of adjustment of resistor 13.

By using such a voltage (e. g. 250 volts D.-C.) at positive pole 13+ that tube 7 operates far below its rated maximum plate current, the curve 23 which corresponds to a low value of resistor 13, leaves the zero-current axis at a cutoff input voltage higher than that impressed on grid 6 by static or other unwanted noise voltages in the output of receiver 4. In other Words, the noise may be rendered or" nov effect on the amplified output by proper adjustment of resistor 13 relative to resistor 14.

In absence of an input signal, the current flow through tube 12 and relay 16 is zero and the ratio of resistor 17 to resistor 18 fixes the potential above ground of the cathode of tube 12 above that of the anode of tube 7. When an arriving signal pulse so raises the potential of the grid of tube 12 that it conducts current, this current, passing through resistor 17, raises the potential of the cathode of tube 12 and so damps the magnitude of current liowing through relay 16 from tube 12. This automatically prevents the current in relay 16 from rising to -a value suificiently to violently bounce its armature against its output contact 24?. I have accordingly provided an electronic amplifier of a type which minimizes bounce in the relay '16.

To give specific instance of the use of the principles of my invent-ion,'the tubes '7 andlZ may be parts of a (BUS tube. the resistors may have the following values in ohms: #9-6.8 l0 #11-4.7 lO #13l0 man; i l4l(l ii l5--l.5 lO"=; #l7--4730; #l8-6.8 l6" the Winding of relay 16 has a resistance of 5,000 ohms; the capacitor #8- l.7- l-0" farads; and the voltage-toground or. terminal 8+ is 259 volts D.-C. The current in the relay coil 16 at closure is 3 ms. and at opening is 1.4 ma.

1 claim as my invention:

1. in combination with a source of voltage pulses, a first electron discharge device having an anode, cathode and at: least two grids included therein, one of said grids being a control grid, meanstor applying said voltage pulses to said control grid, a plate circuit for said discharge device, a first resistor of magnitude in the order or ten t ies the plate resistance of said discharge device included in saidpla'te circuit, a second electron dis harge device having an anode, cathode and grid included therein, a connection between the side of said first resistor n'" est the anode of said first discharge device and the g1 .l. of said second device, means including the energizing coil of a. relay and a resistive impedance element in series connecting thev cathode of said second device to the other side of said first resistor, a further impedance .lement. connecting the junction of said coil and said fi st-- entioned impedance element to the cathode of the st electron discharge device, a second resistor connecting the cathode of said first device to the other grid of said first device, and a third resistor of a magnitude in the order ten times the magnitude of said second resistor connecting said other grid to said other side of the first resistor.

2. in combination with a source of voltage pulses, a first electron discharge device having an anode, cathode and at least two grids included therein, means for applying said voltagev pulses to the one of said grids near-2.; said cathode, a terminal adapted for connection to the positive side of an anode voltage source, the negative side of said voltage source being grounded, a first. resistor of amagnitudedn' the order of. ten times the internal impedanceof said discharge. device connecting said anode to 'said terminahnneans connecting 'said cathode to ground, a second resistor connecting said. other grid to ground, a third resistor of'amagnitude in the order of ten times the magnitude of said second resistor connecting said other grid to saldterminal, a second electron discharge device having an anode, a cathode and a grid included therein, a connection between'the' anode of said first device the grid of said second device, means including a re energizing coil'and'a fourth resistance in series connecting the cathode of said second device to ground, and a fifth resistance connecting the junction of said fourth resistance'and said energizing coil to said termi "References Cited in thefile of this patent UNITED STATES PATENTS 2,084,186 Braden .a Zune ii 193'] 2,343,753 Davey a Mar. 7, 1944 2,564,823 -Wallaceco M Aug. 21, 1951 2,591,810 Hart as" d. Apr. 8, 1952

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